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Author Topic:   Intake Manifold Gasket Restrictors
posted August 22, 2001 10:56 AM
My Fel-Pro intake gaskets came with some small restrictor plates that are optional when installing the intake manifold. (they are small clips designed to insert in the center port hole). I have a 350, mild cam, motor and stock intake. Should I install these restrictors or not? I read in the June issue of Circle Track "The Highs and Lows of a Cooling System" that high flow rates are better for cooling with today's technology. They explained that a faster flow of water and more pressure will keep steam pockets from forming and so on. Any thoughts or opinions? Thank you.

posted August 22, 2001 12:36 PM
What I think you are talking about there are the tin block-off plates that are used to block off the manifold heat risers. Those "ports" are there to circulate hot exhaust gases thru and across the underside of the intake plenum area, thereby heating up the intake sooner and opening the choke sooner in the carb (for street cars, that is).
For racing purposes, these "ports" are typically blocked off during engine assembly and (as you will notice), intakes designed for racing purposes won't have those "ports" in them and therefore those tin "restrictors" aren't needed. The reason for this, is you want the intake (and incoming air/fuel mixture) to remain as cool as possible and not to be any hotter than it has to be.
Now, all of this has really little or nothing to do with the actually cooling system in your motor (or water flow rates, etc) like you were implying. All of that is a book-load in itself. Probably the best place to start is to read up on Stewart's website about cooling systems, and take it from there.

Hope that helps,


posted August 22, 2001 12:38 PM
The center ports are not for coolant,they are for exhaust gas flow for an EGR valve.In a racing application you have no need for this.If you are using an alumninum intake there is probably no opening in the intake for this.If you are using an intake that has an EGR valve, you need to block the opening off completely at the head.I have always cut some small pieces of flat thin metal and siliconed tham in place underneath the intake gasket.This prevents hot exhaust gas from entering the intake which helps to keep the incoming fuel charge cooler and heat away from the carb.

posted August 22, 2001 12:48 PM
Thank you all very much. I'm learning this as I go so forgive my mis leading question. After reading all of your explinations, I now understand what is going on.

What is the best way to completely block off the passage. Some of you suggested to silicone thin sheet metal under the gasket, will that cause any leaks in the other ports?

KPLugnut: what is the address of the site?

Thank you again for the help!

posted August 24, 2001 07:46 AM
Here is the site you are asking about:

And as for the installation of the tin block-off plates, no, if done correctly, and if you silocone both sides of the tin, there should be no leaks there or anyplace else in the intake gaskets.
Good luck, and if you have any other questions, don't hesitate to ask.


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